As is well known to persons skilled in this particular branch of the art, the screen printing of fabrics--whether they be in fabric pieces or finished garments--is carried out by as many printing screens as there are colours which compose the design and/or wording to be printed.
Each screen frame is covered with a gauze with photoengraved perforations which exactly reproduce the portion or portions of one colour of the design and/or wording.
The screen is placed on the fabric and a printing paste of the desired colour is repeatedly spread over the gauze by means of one or more squeegee blades so that, opposite the engravings, the underlying fabric remains printed as a consequence of the extrusion of the printing paste through them. The operation is repeated with all the screens prepared for the different colours composing the design and/or wording which, finally, remains impressed on the fabric.
Automatic machines for the screen printing of fabrics are known which comprise a conveyor belt which is caused to advance stepwise so as to bring each fabric piece or garment opposite the printing screens, which are supported one after the next above the conveyor belt. When the conveyor belt is stationary the screens are lowered onto their respective fabrics and the wheeled squeege blades are drawn to and fro so as to extrude the printing paste through the engravings on the gauze.
In the screen printing of fabrics one technical problem to be solved relates to the centering of the screen with respect to the piece or garment.
In the case of a fabric piece (i.e. a non-finished garment), the aforesaid problem is readily solved by making marks or providing reference means on the conveyor belt, by means of which marks or reference means the fabric piece can be immediately centered with respect to the printing screen. Furthermore, the belt is normally self-adhesive in order to keep the fabric firm during the printing operations.
In the case of a garment, however, for example a T-shirt or the like, the solution is not as simple as this: for the prime condition for a perfect centering of the garment in the desired position with respect to the printing screen is that the garment be placed on the conveyor belt with its parts, i.e. front and back, in a very exact reciprocal position of symmetry. In this case, moreover, the self-adhesive belt cannot keep the whole garment firm in that it can act only on one part of it, that is to say the front or the back.
The above problems are presently solved by using flat forms of wood, plastic or similar material, which are introduced into the garment before the printing process.
Although this system gives satisfactory results, it nevertheless has the serious drawback of requiring excessive manpower: two operators are in effect required, one upstream of the apparatus to place the forms into the garments and one downstream of the apparatus to remove them from the garments.
Additionally, the cost of purchasing and storing the forms is not negligible.